1. Field of the Invention
The present invention concerns a method and device for the regulation of an automatic transmission unit in motor vehicles.
2. Description of the Related Art
As is known, an automatic transmission unit for motor vehicles usually includes a series of several coupling means such as a torque converter, a coupling unit which can be engaged and disengaged and which has a forward coupling and a reverse coupling, and a continuously variable transmission.
The torque converter is driven by the motor, while the continuously variable transmission drives the wheels via a differential.
Both the torque converter, the couplings, and the continuously variable transmission are controlled by hydraulic control means, which in turn are regulated by electronically driven control valves.
As is known, continuously variable transmissions consist of two V-shaped pulleys in between which a V-belt has been applied. Each pulley is formed of two cone-shaped pulley halves which can move in relation to one another, such that the transmission ratio can be altered by axially shifting the pulley halves of at least one of said pulleys either more or less apart, as a result of which the radius upon which the belt on the pulley is situated is altered. The mutual position of the pulley halves is adjusted as a function of different data by means of the above-mentioned hydraulic regulating means which provide for the moving of one of the pulley halves.
The known embodiments are disadvantageous in that when the electronics fail, the regulation of the above-mentioned coupling means is also interrupted. If the vehicle is not equipped with a torque converter it will be either impossible to drive further with the vehicle, or the transmission will be overloaded and ultimately damaged, as for example, due to the slipping of the belt.